1. Field of the Invention
The present invention relates to plant-growing equipment. More precisely, the invention describes an apparatus to enhance aeration of a substrate supporting a plant.
2. Description of the Prior Art
Plants require fundamental elements in order to grow. (These elements are water, various nutrients, and air (more specifically, oxygen). Usually, water and nutrients are well supplied to the plant.
The roots anchor a plant to a substrate, and extract the nutrients therefrom. Artificial substrates are now widely used. They replace common soil. Unfortunately, soil oxygenation is often inadequate in many substrates. A lack of suitable oxygenation can prevent the proper development of a plant. The lack of oxygenation is exacerbated if the particles of the substrate are relatively small. A common approach to the problem is to use substrates that have large particles, but such substrates are costly. The bottom of a typical plant-growing container is often subject to a lack of oxygenation. As roots reside in the bottom of plant-growing containers, the proper oxygenation of bottom portions of containers can help in optimizing the development of plants.
In order to overcome the under-oxygenation of the roots, various solutions have been tested. One solution consists in creating aeration holes on the walls of plant-growing containers. These aeration holes then allow the natural airflow and thus the oxygenation of bordering areas of a substrate. For instance, U.S. Pat. No. 4,528,774, issued to Skaife on Jul. 16, 1985, and U.S. Pat. No. 954,440, issued to Klemm on Apr. 12, 1910, each describe plant-growing containers having perforations on their lateral surfaces supporting the substrate.
British Patent No. 403,460, issued to Roberts et al. on Dec. 28, 1933, U.S. Pat. No. 4,173,098, issued to Smith on Nov. 6, 1979, and U.S. Pat. No. 4,236,351, issued to Smith on Dec. 2, 1980, each disclose plant-growing containers defining a cavity below a substrate section. The cavity and the substrate section are separated by a perforated disk allowing an air supply to the bottom of the substrate section. Cylindrical tubes extend through the substrate section to reach the cavity and supply water thereto. Ambient air can also circulate through the cylindrical tubes to reach the cavity. Furthermore, in British Patent No. 403,460, the cylindrical tubes are perforated in their portion embedded in the substrate section, such that the substrate can be oxygenated through these perforations.
German Patent No. 806,918, issued on Jun. 21, 1951 to Kiel, and U.S. Pat. No. 1,952,597, issued to Lizzola on Mar. 27, 1934, both describe devices that are securable to an inner wall of plant-growing containers. These devices are perforated and allow the oxygenation of the substrate. These devices can take various shapes, including an upwardly flaring cone.
U.S. Pat. No. 3,958,366, issued to Meyers on May 25, 1976, discloses a plant-growing container that permits the irrigation of the substrate as well as the aeration thereof. The aeration is effected by cylindrical tubes that project from the exterior surface of the plant-growing container towards the substrate. These cylindrical tubes are perforated, such that air can be supplied to the substrate.
U.S. Pat. No. 4,175,356, issued to Allen on Nov. 27, 1979, describes a cylindrical tube having pointy ends to be inserted into the substrate of a plant-growing container. The cylindrical tube defines an inner cavity on a full length thereof, and the peripheral surface of the cylindrical tube is perforated, such that the substrate into which the cylindrical tube is inserted can be oxygenated by the air contained in the inner cavity. The pointy ends of the cylindrical tube are also perforated, such that ambient air can fill the inner cavity. The cylindrical tube is simply inserted into the substrate and the pointy ends facilitate the insertion.
U.S. Pat. No. 5,692,338, issued on Dec. 2, 1997 to Rose, describes a device similar to that of U.S. Pat. No. 4,175,356 in that the device can be inserted into the substrate by a pointy end. However, the device disclosed in U.S. Pat. No. 5,692,338 is shaped as a square-based pyramid, inverted when inserted into the substrate.
In the above-cited references, the diffusion rate within the aeration structure cannot be modified, as the devices are passive (only provide diffusion of air). However, considering that the aeration demand may vary in time because of an increased soil biological activity, of the evolution of the physical properties of the soil, or of a more active root growth, devices that will improve the aeration process rapidly and efficiently must be introduced.